Now I'd like to add notes on my document.
To enter text, you need to create a special text region by clicking on the text button on the tool bar.
A text region appears.
You can move around in this region using the arrow keys and the Enter, End, Home, and Tab keys.
To exit a text region, simply click outside of it, and Mathcad's ready to work with math.
To edit a text region, click on it. You automatically switch to text mode. Let's delete "and" and type in "are".
Well, Addie, that's a basic introduction to how to use Mathcad. 
And remember, Mathcad comes with on-line help and a User's Guide to answer your questions.